There are many processes where a need exists to extract liquid from sludges, slurries, or the like. As examples, these processes are found in food processing, sewage disposal, oil well drilling mud recovery, brewing, paper making, mining, waste disposal and the like. In many applications the use of apparatus which is integral and which is portable or readily movable is advantageous or necessary.
The terms slurries, sludges, and sediments may be used interchangeably in this description. Also, the terms particles, bits and pieces may be used interchangeably herein to designate the solids either suspended or separated from liquid.
The presently known prior art consists of the following: U.S. Pat. No. 332,718 to Lafferty shows liquid extraction apparatus having a tapered screw rotatable within a tapered screen with the screen mounted in a slotted housing to drain squeezed out liquid. No. 3,176,606 to Zoffman shows an inclined screw and screen arrangement to extract beer wort from the hops leaves. No. 3,688,687 to Craig et al shows an inclined screw and screen arrangement to extract water from chopped trash. No. 3,768,171 to Bird et al shows a horizontal tapered screw rotatable in a tapered housing to remove water from rubber scraps. No. 4,214,377 to Maffet discloses a horizontal screw rotatable in a circumferentially slotted screen to extract water from sewage sludge or wood pulp chips. No. 3,426,677 to Combes et al discloses an inclined screw rotatable within a screen to extract water from a slurry of wet solids. No. 4,297,208 to Christian shows an inclined interrupted screw having drain openings along the shaft and being rotatable within a housing to extract water from a suspended slurry.
More comprehensive information concerning liquid-solid separation of the different kinds is available in the book by Svarovsky, Ladislav, "Solid-Liquid Separation" Butterworths, London, 1977, and in "Process Design Manual For Suspended Solids Removal", U.S. Environmental Protection Agency Technology Transfer, E.P.A. 625/1-75-003a, Washington, D.C., January 1975.
The tapered extractor screen described herein may be manufactured for this invention by Johnson Division, Signal Applied Technology, Inc., 1950 Old Highway 8, St. Paul, Minnesota 55164, for example and is of a type referred to under Johnson's trademark as a "Vee-Wire" screen.
The "Red Valve" valves provided herein may be provided as specified for example by Red Valve Company, Inc., 600 North Bell Avenue, Carnegie, Pennsylvania 15106.
The term portable apparatus, as used herein, means apparatus integrally mounted on a common skid type base and which can be loaded, transported, unloaded, and placed into service as an integral unit.